Production of aromatics



Jan. 29, 1957 P. T. SOWDEN, JR

PRODUCTION OF AROMATICS Filed Fab. 18, 1952 TO RECOVERY P ROCESS FEEDINERT GAS BY PRODUCT COKE INVENTOR.

P. T. SOWDEN,JR.

A TTOEWEYS United States Patent This invention relates to i theproductibii 'of "aromatics;

In one"of=its moreispecific aspects, this invention-relates toapr'oce'ss for the productionof aromatics by pyrolysis of lighthydrocarbons. In another of its more' specific aspects, -it=relates tonew apparatus"for carrying out=the processw In-a'nother of its morespecificaspebts, it relate's tea-method ofand apparatus for theproduction of aromatics-Ebypyrolysis of light hydrocarbons in whioh itis possible-to controlindependently the oper'ation'of 'a soaking'zoneand quench zone. i

In conventional cracking processes in which aromatics are produced bypyrolysis of hydrocarbons; a gaseous hydrocarbonfeed is heated in anespecially designed furnace after which the heated gases are passed to asoaking chamber wherein furthercracking and polymerization reactionstake place. This'soaking chamber has generally consistedof an emptyvessel. 7 One of the difliculties experienced in this process is thatpai't of the material is broken down to coke and tars; Part ofthese-materials deposit infthe chamber and another part is carried alongwith thegas stream and cause difficulties suchas plugged transfer linesand stopped valves. As a result, numerous pl ant s hut downs occur whilethe carbon and tar is removecllfrom the soalting chamber and otherequipment, whicli isiisual-ly done' by burning'the carbon withacontrolledstrearn of air. r i

By the various aspects of this invention, one or more of the fbllowiiigobjectswill'b'e obtained.

A n objec t of this invention is an improved method for the pfoductionof area-rates. A further object of this invention' is an improved methodfor the production ofaromatics by pyrolysis of light hydrocarbons. Afurther object of this invntioiris to provide new apparatus for the"production of aromatics A still'fiir'the'f o'bj'e'c't o'f thisinvention is to" pr'ovide' said apparatus in which'it is possible tocontrol independently the soaking and quenching operation's' involved inthe cracking process. Further objects will'be apparent to one skilled'inthe art ou examinationbf the accompanying disclosure.

The drawing presents a flow sheet of a preferred embodiment of'myinve'en. t i n V t l invntionfhydrocarbonsare treated ih the vapor sisting'principally'of benzene, toluene; and xylene, and a -heavy oil fraction"containing higher members of the aron iatic' ser'ies seen asnaphthalene; lnfhitcene, phenanthriief'and higher members; as well asalky'l derivatives of the above compounds! The light oil produced bythis process is apprtiximately85"% benzene. Where prior processes haveconsidered coke arid'tar formation-as a detriirient iii the process,Ihavedeveloped a processwherem-a-fomiationer coke is taken advantage of,and this coke is collected asaby-product of the process.

In the proceSsQ tlie hydrocarbon feed is preheated and are allowedtoreact-in contact with a moving bed of action products are fed to thesoakingzonell 'Where the ice coke particles or pellets; These cokeparticles=serve primarily as a condehsing surface on which heavyhydrocarbons degenerate to coke. This moving bed'aliso serves'totrap'coke ortar particlesand this results in a cleancra ckedgas whichwill not plug transferwlines and other equipment.

Following soaking; the gases are conductedto'a suitable quench zonewherein undesirable siderea'ctions are prevented. V

The carborior coke from the soaking zone is treatedso as to recover theheat thereinypatt of the carbon can be removed as a by-product, and'thebalance recirculated through the system.

Novel features of my invention will become apparent upon considerationof the accompanying drawingwheree in the apparatus is shown in detail.The principalzones of this apparatus consist ofa quench zone 10, a'soaking zone 11, and a pellet temperature control zone 12, which may be ofany shape but are generally circular in cross section; andare closed attheirupper and lower ends except where inlet and outlet conduits,hereafter discussed, are provided. An elevator, such as gas-lift 13 ispro vided which eittends from a level below the lowermost part ofchamber 12 toa levl above the uppermost part of chamber 110, and servesto convey circulating material upwardly. Pressurizer 14 is connected tothe lower end portionof gas-lift 13 bymeans of conduit 16, and totheupper end of said gas-lift by means of conduit 17. Solid materialconduit 1% connects the upper end piortionof"gas-lift 1'3 and'the'uppe'rend portion of chamber 11), and conduit 19 connects the lower endportion of chairlber 12 with theilowerjend portionof gas-lift 13,conduit 19 "being provided with flow controller '21 andrniovalcoiiduitflzt Conduit'23 extends from the lower endfportion ofch'anibe'rit) to'theupperend portion of chamber llandjco u it24jproyided with fiow controller 25, eit tendsffrom' flowerendportion'of chambert ll to the "upprendp'ortion of chamber 12. Bypass conduit 26 extends between conduits23 'arid 24 and is pro vided'withmy prenew? controller 27, said controller 27 beingldcafedheaf'the pointatwhich conduit 26 con nects withcbiidiiit"2 l The fiow coiitrollers areillustrated as starves but slide valves or known types of valves can beused; i

F rna'ce zsis pmvided to prelreat the feed, said'feed being pa'ss'e tothe coils29*of said furnace by means of conduit '31. Conduit 32 extendsfromthe furnace and dividesinto conduit fiia, communicating with thelower end of zone'11', and conduit 34:; communicating with the upper endof zone: ii -1, said latter conduits being provided with valves '36and'37. Conduit 38 communicates with the lower end-of zone ll andconduit '39 communicates with the upper end of zone 11, said conduitsjoining to form conduit 41, said conduit communicating with thelowerend-por'tion'of zone 10. Valves'42 and43 are provided in conduits38 and 39, respectively. Conduit 44 extends frofrfthe uppergen'd'portionof zone 10.

Waste heat recovery boiler 46 is provided near zone 12 and is connectedto zone 12 by means of conduit 47. Conduit 48 is provided extending intothe lower portion ofzone'12.

In the operation of'my process; the hydrocarbon feedstream to be crackedis passed through the coils 29 of furnace 28 where it is preheated. Thisis essentially a rapid heat transfer process and is conducted atpressure slightly aboveatmospheric;' Thereafter, the heated remajor partof the'reaction takes place, after which they are conducted to que'n'chzone 10. I prefer to use concurrentflow the soaking zone, i e.passingthe gas into the upper portion of said zone through conduits 32and 34,-and utilizing conduits 38'and 4l to convey the products to thequench zone. However, the apparatus is designed so that countercurrentflow can be carried out by passing the products from the furnace 28 tothe soaking zone 11 through conduit 33 and removing these products fromzone 11 by means of conduit'39. Concurrent flow generally providesbetter control in the soaking zone.

Coke pellet flow in this process is as follows, starting arbitrarilywith quench zone 10. As hereafter described, the pellets supplied tothis zone should be cooled to a temperature low enough to quench theproducts to a temperature so that no further reactions will occur in theapparatus following this zone. From zone the pellets flow downwardly bygravity through conduit 23. A portion of the pellets flow into soakingzone 11 and generally a major portion is by-passed around zone 11 bymeans of conduit 26. The coke pellets which are passed tothe soakingzone 11 serve primarily as a condensing surface on which heavyhydrocarbons may degenerate to coke. The moving bed also serves to trapcoke or tar particles, thus generating a clean cracked gas which Willnot foul the transfer lines and subsequent equipment. Coke particles areremoved from zone 11 and, in combination with the pellets passed throughby-pass conduit 26, flow by gravity into pellet temperature control zone12. In this zone, the major portion of the heat contained in the coke isremoved therefrom. I prefer to remove this heat by direct contact withan inert gas supplied by conduit 48, which subsequently generates steamin an outside heat recovery unit 46. However, the heat may be removedindirectly by water or gas circulation in tubes or other suitable heattransfer surface. This step enables me to control the temperature of thecoke pellets supplied to the heating zone.

Thecooled pellets are removed from the lower end of pellet temperaturecontrol zone 12 by means of conduit 19 which is connected to the lowerend of gas-lift 13. By means of flow controller 21, the amount of cokepassed through gas-lift 13 is controlled. By-product coke is removedfrom line 19 through conduit 22. This coke is utilized as chemical orelectrode carbon, or burned as a refinery fuel, as desired.

An important aspect of my invention is by-pass conduit 26 and theadvantages in operation which are obtained thereby. This permits controlof the amounts of materials in the soaking zone and the quench zone,that is, a large amount of pellets can be circulated through the quenchzone so as to provide for rapid quenching, while a much smaller amountof coke is passed into the soaking zone. In this invention, thecirculation rate through the soaking zone may be varied at will whilecirculating a constant amount of material through the quench zone.Without the feature of this by-pass, the rate required for quenching isoften too high for optimum soaking conditions. Flow controllers 25 and27 cooperate to regulate pellet flow. Frequently flow controller 27 isleft in full open position and flow controller 25 provides adjustmentnecessary for proper control of pellet residence time in chamber 11.

An advantage of a quenching zone of this type over the conventionaldirect oil or water quench is that this quench zone employing thecirculating coke enables recovery of the heat which is contained in thegaseous products. Furthermore, as stated above, a cleaner product isobtained as well as the additional product, that is a good grade ofpetroleum coke. a 7

Should operations require such a low depth of cracking that the net heatof reaction was endothermic, heat could be supplied to the coke by inertgases and the coke would then become a heatingmedium.

The apparatus of this invention can be used for various types ofcracking reactions, one of the most important being the cracking ofnormal butane to produce aromatic hydrocarbons and coke. In order thatthis invention may be fully understood, the following discussion relatesto 4 such a process; the temperatures and pressures being dis closedtherein are given by way of explanationand are not to be considered aslimiting conditions.

Example A normal butane feed is vaporized and passed through tubecracking furnace 28 under conditions such that substantial quantities ofethylene and propylene are produced. Preferred conditions areatmospheric pressure or a few pounds thereover, a contact time of onesecond, and an effluent temperature of 1400 F. The furnace effl uent ispassed through conduit 34 and into soaking chamberll in concurrent flowwith a moving bed of granular coke, at a rate such that a contact timeof 24 seconds is obtained. Under these conditions a substantialconversion of olefinic hydrocarbons occurs, accompanied by a release ofheat due to the exothermic reactions occurring, and the coke andhyrdocarbons leave the soaking zone 11 by means of conduit 38 at atemperature of about 1500 F. The hydrocarbons are passed into the quenchchamber 10 where they flow concurrently through the bed of granular cokeand are quenched to about 600 F., said temperature being sufficientlylow so that all further reactions are substantially stopped. Theproducts can then be further cooled or condensed by conventional meansto a temperature suitable for recovery and purification. Coke pelletswithdrawn from the lower portion of the quench zone 10 are divided intotwo streams; a minor portion, which may be as small as one percent byweight, passes to the soaking chamber and the remainder pass directly tothe pellet temperature control zone 12. These coke pellets, which are ata temperature of approximately 1400 F. are combined with the cokepellets from soaking zone 11 and contacted with a cooled inert gasentering said zone through conduit 48. Coke leaves the pellettemperature control zone 12 at a temperature in the neighborhood of 600F., and the inert gas, which is heated to about 1300 F. is passedthrough conduit 47 to waste heat boiler 46 for the production of steam.

Typical compositions for the various streams in the process are shown inthe following tabulation. This shows the products obtained whenoperating the above process at a feed rate of 1000 barrels per day.

Furnace Efliuent Soaker Eflluent Component Wt. Per- Lbs/Day Wt. Per-LbsJDay cent cent 7 Heavy Oil 3.1 6, 340 11. 9 24, 350

The treatment conditions, of course, depend upon the particular materialbeing treated. When operating on the specific feed stream mentionedabove, I prefer to operate a furnace so that the output gas will have atemperature of 1200 to 1600" F. and more preferably 1400 to 1500 F., anda pressure of 2 to 15 p. s. i. g. Under these conditions, the length oftime in the furnace can be one second or less, which eliminates carbondeposition within the tubes of the furnace. The reaction time in thesoaking zone is dependent to a very large extent upon the temperaturetherein. Considering the furnace temperatures stated above, it should bepointed out that at 1400 F. the products will be the same with a 24second reaction time as those obtained at 1500 and a reaction time of 3seconds. The pressure in the soaking zone should be approximately thesame as that in the furnace.

The coke circulation rate depends entirely uponthe;

1 circulation rate is approximately 25,000 pounds per hour. 1 Thus, itis apparent that I have invented a new process and apparatus for theproduction of aromatics. A subvprocess can be recovered at a hightemperature level, this being due to the fact that heat is transferredfrom the products to the circulating carbon pellets in the quench zoneand in the soaking zone, and the heat is removed from the system by theinert gas stream in zone 12. My process enables me to produce a cleanhydrocarbon product and a good grade of petroleum coke.

As many possible embodiments may be made of this invention withoutdeparting from the scope thereof, it is to be understood that all matterherein set forth or shown in the accompanying drawing is to beinterpreted as illustrative and not in a limiting sense.

I claim:

1. Apparatus for hydrocarbon cracking and reforming comprising a firstchamber; a second chamber below said first chamber; a first conduitconnecting the lower end portion of said first and the upper end portionof said second chambers; a third chamber below said second chamber; asecond conduit connecting the lower end portion of said second and theupper end portion of said third chambers; a third conduit connecting thelower end portion of said first chamber and the upper end portion ofsaid third chamber; an elevator extending from a level below the lowerend portion of the third chamber to a level above the upper end portionof the first chamber; a fourth conduit connecting the lower end portionof said third chamber and the lower end portion of said elevator; aproduct removal conduit communicating with said fourth conduit; a fifthconduit connecting the upper end portion of said elevator and the upperend portion of said first chamber; means for passing fluid heat exchangematerial through said third chamber; a sixth conduit communicating withone end portion of said second chamber; a heater in said sixth conduit;a seventh conduit connecting the second end portion of said secondchamber with the lower end portion of said first chamber; and an eighthconduit extending from the upper end portion of said first chamber.

2. The apparatus of claim 1 in which said elevator comprises a gas lift.

3. The apparatus of claim 1 in which a flow controller is provided insaid second conduit.

4. The apparatus of claim 1 in which a flow controller is provided insaid third conduit.

5. The apparatus of claim 1 in which the means for passing fluidmaterial through said third chamber comprises a conduit extending intothe lower portion of said chamber and a conduit extending from the upperportion of said chamber; and a heat exchanger located downstream of saidthird chamber.

6. Apparatus for hydrocarbon cracking and reforming comprising a firstchamber; a second chamber below said first chamber; a first conduitconnecting the lower end portion of said first and the upper end of saidsecond chambers; a third chamber below said second chamber; a secondconduit connecting the lower end portion of said second and the upperend portion of said third chambers; a flow controller in said secondconduit; a third conduit connecting the lower end portion of said firstand the upper end portion of said third chambers;

a flow controller in said third conduit; a gas-lift extending from alevel below the lower end portion of said thirdchamber to a level abovethe upper end portion of the first chamber; a fourth conduit connectingthe lower end portion of said third chamber and the lower end portion ofsaid gaslift; a product removal conduit communicating with said fourthconduit; a fifth conduit connecting the upper end portion of saidgas-lift and heat load, which is determined by the feed rate and re-...act1'on conditions. In the above example, where a thousand barrels aday of butane are being treated, the coke the upper end portion of saidfirst chamberyasixth-con duit extending into one end portion of saidthirdcham= her; a seventh conduit extending from the other; end

. stantial portion of the heat required or generated in the p i portionof said third chamber; aheat exchangeniii said seventh conduit; aneighthconduit communicating with one end portionof said second chamber; afurnace located in saideighth conduit; a ninthc'onduit connecting thesecond end portionof said second chamber and the lower end portion ofsaid first chamber; and" a tenth conduit extending from the upper endportion of said first chamber.

7. A method'ofhydrocarbon cracking and reforming comprising introducingrelatively cool coke-pellets into aquenching"zone;"gravitating saidpellets from thelower portion of said zone; dividing said pellets intofirst and second portions; passing the first portion into the upperportion of a soaking zone; passing a hydrocarbon stream in gaseous formwhich has been preheated to reaction temperature into said soaking zone;thereafter passing a resulting product stream from said soaking zone tosaid quenching zone; removing the quenched gaseous product from theupper end of said quenching zone; gravitating said coke pellets from thelower end of said soaking zone; combining said first and second portionsof said pellets; passing said combined stream of pellets into a pellettemperature control zone; cooling said pellets in said zone with a heatexchange fluid; gravitating said pellets from the lower portion of saidpellet temperature control zone; elevating said pellets from the lowerend portion of said pellet temperature control zone to an upper endportion of said quenching zone; and removing a portion of said pelletsas a product of the process.

8. A method of hydrocarbon cracking and reforming comprising introducingcoke pellets at a temperature of approximately 600 F. into a quenchingzone; gravitating said pellets from the lower portion of said zone;dividing said pellets into first and second portions; passing the firstportion into the upper portion of a soaking zone maintained at atemperature of from 14-00" F to 1500 F.; passing a hydrocarbon stream ingaseous form which has been preheated to a temperature of approximately1400 F. into said soaking zone; passing a resulting gaseous productstream from said soaking zone to said quenching zone; removing aquenched gaseous product from the upper end of said quenching zone;gravitating the coke pellets from the lower portion of said soakingzone; combining said first and second por-- tion of said pellets;passing said combined stream of pellets into a pellet temperaturecontrol zone; cooling said from the lower portion of said pellettemperature control zone; introducing said pellets into the lowerportion of a gas-lift zone; lifting said pellets in said zone; fromwhich zone said pellets are passed to said quenching zone, thuscompleting a pellet cycle; and removing a portion of said pellets as aproduct of the process.

9. The method of claim 7 in which heat is recovered from the heatexchange fluid which is heat exchanged with the pellets in said pellettemperature control zone.

10. A method of hydrocarbon cracking and reforming comprisingintroducing coke pellets at a temperature of approximately 600 F. into aquenching zone; gravitating said pellets from the lower portion of saidzone; dividing said pellets into first and second portions; passing thefirst portion into the upper portion of a soaking zone maintained at atemperature of from 1400' F. to 1500 F.; passing a hydrocarbon stream'ingaseous form which has been preheated to a temperature of approximately1400 F. into said soaking zone; passing a resulting gaseous productstream from said soaking zone to said quenching zone; removing aquenched gaseous product from the upper end of said quenching zone;gravitating the coke pellets from the lower portion of said soakingzone; combining said first and second portion of said pellets;

passing said combined stream of pellets into a pellet temperaturecontrol zone; cooling said pellets to a temperature of approximately 600F. by heat exchange with an inert gas; gravitating said pellets from thelower portion of said pellet temperature control zone; introducing saidpellets into the lower portion of an elevating zone; lifting saidpellets in said elevating zone, from which zone said pellets are passedto said quenching zone. thus completing a pellet cycle; and removing aportion of said pellets as a product of the process.

References Cited in the file of this patent UNITED STATES PATENTS2,389,636 Ram-seyer Nov. 27, 1945 55 Happel Apr. 13, 1948 Simpson Sept.7, 1948 Huff Mar. 8, 1949 Crowley Apr. 5, 1949 Utterback et al. July 26,1949 Arnold Nov. 1, 1949 Crowley Dec. 6, 1949 Johnson Jan. 3, 1950 GarboOct. 24, 1950 Ardern July 24, 1951 Quigg et al. Oct. 23, 1951

1. APPARATUS FOR HYDROCARBON CRACKING AND REFORMING COMPRISING A FIRSTCHAMBER; A SECOND CHAMBER BELOW SAID FIRST CHAMBER; A FIRST CONDUITCONNECTING THE LOWER END PORTION OF SAID FIRST AND THE UPPER END PORTIONOF SAID SECOND CHAMBERS; A THIRD CHAMBER BELOW SAID SECOND CHAMBER; ASECOND CONDUIT CONNECTING THE LOWER END PORTION OF SAID SECOND AND THEUPPER END PORTION OF SAID THIRD CHAMBERS; A THIRD CONDUIT CONNECTING THELOWER END PORTION OF SAID FIRST CHAMBER AND THE UPPER END PORTION OFSAID THIRD CHAMBER; AN ELEVATOR EXTENDING FROM A LEVEL BELOW THE LOWEREND PORTION OF THE THIRD CHAMBER TO A LEVEL ABOVE THE UPPER END PORTIONOF THE FIRST CHAMBER; A FORTH CONDUIT CONNECTING THE LOWER END PORTIONOF SAID THIRD CHAMBER AND THE LOWER END PORTION OF SAID ELEVATOR;APRODUCT REMOVAL CONDUIT COMMUNICATING WITH SAID FOURTH CONDUIT; A FIFTHCONDUIT CONNECTING THE UPPER END PORTION OF SAID ELEVATOR AND THE UPPEREND PORTION OF SAID FIRST CHAMBER; MEANS FOR PASSING FLUID HEAT EXCHANGEMATERIAL THROUGH SAID THIRD CHAMBER; A SIXTH CONDUIT COMMUNICATING WITHONE END PORTION OF SAID SECOND CHAMBER; A HEATER IN SAID SIXTH CONDUIT;A SEVENTH CONDUIT CONNECTING THE SECOND END PORTION OF SAID SECONDCHAMBER WITH THE LOWER END PORTION OF SAID FIRST CHAMBER; AND AN EIGHTCONDUIT EXTENDING FROM THE UPPER END PORTION OF SAID FIRST CHAMBER.
 7. AMETHOD OF HYDROCARBON CRACKING AND REFORMING COMPRISING INTRODUCINGRELATIVELY COOL COKE PELLETS INTO A QUENCHING ZONE; GRAVITATING SAIDPALLETS FROM THE LOWER PORTION OF SAID ZONE; DIVIDING SAID PALLETS INTOFIRST AND SECOND PORTIONS; PASSING THE FIRST PORTION INTO THE UPPERPORTION OF A SOAKING ZONE; PASSING A HYDROCARBON STREAM IN GASEOUS FORMWHICH HAS BEEN PREHEATED TO REACTION TEMPERATURE INTO SAID SOAKING ZONE;THEREAFTER PASSING A RESULTING PRODUCT STREAM FROM SAID SOAKING ZONE TOSAID QUENCHING ZONE; REMOVING THE QUENCHED GASEOUS PRODUCT FROM THEUPPER END OF SAID QUENCHING ZONE; GRAVITATING SAID COKE PALLETS FROM THELOWER END OF SAID SOAKING ZONE; COMBINING SAID FIRST AND SECOND PORTIONSOF SAID PELLETS; PASSING SAID COMBINED STREAM OF PELLETS INTO A PELLETTEMPERATURE CONTROL ZONE; COLLING SAID PELLETS IN SAID ZONE WITH A HEATEXCHANGE FLUID; GRAVITATING SAID PELLETS FROM THE LOWER PORTION OF SAIDPELLET TEMPERATURE CONTROL ZONE; ELEVATING SAID PELLETS FROM THE LOWEREND PORTION OF SAID PELLET TEMPERATURE CONTROL ZONE TO AN UPPER ENDPORTION OF SAID QUENCHING ZONE; AND REMOVING A PORTION OF SAID PELLETSAS A PRODUCT OF THE PROCESS.